55.2-59 Turbo 400 kick down question

[toymanbob]

I've found a wire attached to the trans and assume it's related to kick-down. Is it triggered by 12V and from where? Bob

[mr48chev]

Best idea is to check the wiring diagram for the donor rig. Or search out Turbo kick down switch or passing gear switch.

[dsraven]

turbo 400 has an electric switch activated by the accel pedal inside the cab normally. it is 12v fused supply from a "hot with key in run" fuse box connection. just google the topic for a few images of what the switch normally looked like and what the aftermarket hotrod suppliers are supplying.

[mr48chev]

The switch can be inside the cab connected to the gas pedal or on the throttle linkage at the carb.

https://www.ebay.com/itm/12598909698...G090XKZ6B0HAFJ

https://www.ebay.com/itm/13467992884...YaAizlEALw_wcB


The switch for the Edelbrock carb would probably be the simplest to hook up on a truck. The other switch goes on the throttle pedal assembly and you pretty well have to use the whole assembly.

The style in the photo was used on Oldsmobiles a lot but you have to have the lever on the carb designed for it.

[dsraven]

It's a simple switch. There are lots of variations you could use. Back in the day as a heavy duty mechanic Mack trucks used a simple micro switch on the linkage in order to operate the Jake brake. It had a built in diode to stop reverse power flow from energy developed when the magnetic fields collapsed in the Jake actuator solenoids

[dsraven]

this is what they looked like just for reference. a switch similar to this could be easily placed on the throttle linkage so that the kickdown would operate properly. not necessarily this switch but you get the idea

https://www.ebay.com/p/2099396414

here is a thread that discusses the kickdown switches. it is interesting that some are operated by a chain that lookslike a tub drain plug chain. whatever works and has longevity I guess. i seem to remember Ford had a similar set up

https://67-72chevytrucks.com/vboard/...d.php?t=679916

[mr48chev]

Ebay sellers are nuts on used OEM Chevy kick down switches. Only for the restorer shooting for a 100 point car.

Personally I'd look into the 30 something buck micro switch. I may have to get one of those for my 71 GMC with the Cad 500 in it. I want to get it running and driving before winter.

[1project2many]

With a BBC installed, it seems like someone must have replaced the original gas pedal with one from another vehicle? Here's a square body truck gas pedal with a THM 400 kickdown switch. The switch is near the top of the picture. It's the tan parts.


This one is for sale for $25 from a guy in PA.
https://www.hillbillywizard.com/cucv...bly-for-th400/


If you use a microswitch or other low current device you might want to consider using a relay to go with it.

If you have a column mounted dimmer switch you could use the old floor switch to control kickdown. I have done this and it can be nice to force downshift at light throttle for a little help accelerating or going uphill.

Loving the heater bypass hose.